is_a

add a note User Contributed Notes

martin dunisch
14-Feb-2006 04:02


Workaround for older PHP-Versions:



function is_a($anObject, $aClass) {

   return get_class($anObject) == strtolower($aClass)

     or is_subclass_of($anObject, $aClass);

}

dead dot screamer at seznam dot cz
07-Feb-2006 03:44


Why I test if class `A` inherit class `B` or implements interface `C` before I create class `A`?



<?

//That isn't work:



//1. function is_A()

if(is_A('A','B'))$a=new A;

if(is_A('A','C'))$a=new A;



//2. operator instanceOf

if(A instanceOf B)$a=new A;

if(A instanceOf C)$a=new A;

?>

zabmilenko at hotmail dot com
08-Oct-2005 08:20


In the below example, the object and class name need to be reversed.  Sorry.



Wrong:

'ObjectA', $objecta



Right:

$objecta, 'ObjectA'

zabmilenko at hotmail dot com
08-Oct-2005 08:18


Lazy Instantiation using is_a() and php5



<?php



class ObjectA

{

    public function print_line($text)

    {

        print $text . "\n";

    }

}



class ObjectB

{

    public function ObjectA()

    {

        static $objecta;



        if (!is_a('ObjectA', $objecta))

        {

            $objecta = new ObjectA;

        }



        return $objecta;

    }

}



$obj = new ObjectB;

$obj->ObjectA()->print_line('testing, 1 2 3');



?>



In the above example, ObjectA is not instantiated until needed by ObjectB.  Then ObjectB can continually use it's creation as needed without reinstantiating it.  



There are other ways, but I like this one :-)

cesoid at yahoo dot com
06-Oct-2005 10:01


is_a returns TRUE for instances of children of the class.



For example:



class Animal

{}



class Dog extends Animal

{}



$test = new Dog();



In this example is_a($test, "Animal") would evaluate to TRUE as well as is_a($test, "Dog").



This seemed intuitive to me, but did not seem to be documented.

aidan at php dot net
21-May-2004 10:11


This functionality is now implemented in the PEAR package PHP_Compat.



More information about using this function without upgrading your version of PHP can be found on the below link:



http://pear.php.net/package/PHP_Compat

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